Fiber optic couplers are useful in a variety of applications to transfer light from one optic fiber to another, especially in place of a beamsplitter in interferometrics where coherent separation or combination of light is required. In one example described in U.S. Pat. No. 4,280,760, such a coupler is used in an optical gyroscope to split a coherent lightbeam into two equal portions that travel in opposite directions about a loop and are then recombined to detect their phase difference; the interferometric pattern representing phase difference, is proportional to the rotation rate of the loop. Substantial practical difficulties have been involved in fabricating single mode fiber optic waveguide couplers. One approach has been to embed a pair of fiber optic waveguides, or optical fibers, into blocks, to lap away controlled amounts of the optical fiber claddings, and to then place the lapped cladding surfaces into contact with each other. Since a typical optical fiber is of very small size, very small tolerances must be maintained, which makes this coupling technique a difficult and costly one. In another technique, the claddings of two optic fibers are largely removed by etching, and the fibers are then twisted about one another to provide a coupling contact length which is variable with the number of twists. This approach results in a fragile device, and does not preserve the polarization state of the light transmitted between the optic fibers. A technique for coupling a pair of optical fibers in a manner that avoided critically precise fabrication operations, which enabled close control of the amount of coupling, which preserved the polarization state of the coupled light, and which resulted in a reliable device, would be of considerable value.